In order to monitor the wear of a tire, it is known to use depth gauges comprising a probe able to engage into each groove of a tire, a bearing face able to come into contact with the peaks of the ribs and a means of reading giving the depth of engagement of the probe in the groove.
Such gauges are either mechanical, in which case the reading is effected on a graduated scale, or electronic, in which case they comprise means converting the position of the probe into an analog or digital electrical signal, means of processing and of calculation and means of display of the result of the measurement.
The device described in the U.S. Pat. No. 4,631,831 also comprises means memorizing the values of each measurement, calculating the mean value of these measurements and transmitting this result to the means of display.
Such an apparatus thus provides the mean value, expressed in millimeters, of the depth of the ribs and, consequently, merely indicates a value relating to the wear of the tire permitting management of a fleet of vehicles.